The present invention relates to an automatic track finding (hereinafter, referred to as an ATF) circuit having the tracking servo functions in a rotary digital audio tape recorder (hereinafter, referred to as an R-DAT) and more particularly, to an ATF locking circuit which improves the stability of the whole servo system by checking the ATF locking state to cause tracking servo action.
Generally, the ATF circuit having functions for automatically performing the tracking during the playback uses the ATF signal that is included among the radio frequency (hereinafter, referred to as "RF") signals. The standard format of the R-DAT tape is shown in FIG. 1. The digital audio tape recorder using the digital audio tape having the standard format shown in FIG. 1 as a recording medium generates a variety of pulses shown in FIG.2, to automatically carry out the ATF. The ATF block in the digital audio tape recorder detects an ATF synchronizing signal such as FIG. 2a from the reproduced RF signal, and produces sampling pulses such as FIGS. 2e to 2h of for generating the ATF voltage to detect the pilot signal level such as FIG. 2b on the ATF track pattern of the before-and-after tracks. The ATF block samples and holds (hereinafter, referred to as SH) the pilot signal amplified and detected by the sampling pulse to produce the ATF error voltage and controls the position of the head on the track in response to the ATF error voltage. Also, FIG. 2d is a discharge pulse. That is, the tracking error (TE) signal is generated by the pilot signal level of the track, itself, where the head passes, and the pilot signal level of the adjacent track. Thus, if the head is not positioned at the center of the track and leans to one direction, a difference from the pilot signal level of the adjacent track is generated. The ATF block detects the difference and supplies the difference to the capstan motor, thereby controlling the head to trace the center of the track. Since the actual head is one and half times as large as the track width, crosstalk of the data recorded on the adjacent track is possible.
Errors can be generated during tracking, and if there is an index which can show whether the tracking is carried out correctly or not, the problems caused by the generation of errors can be easily solved because the current tracking state can be known and the control that can return to the tracking to a normal state is made possible.